Trying to boot custom kernel on Wink Hub (i.MX28)

[Fabio Estevam]

Hi Rogan,

On Fri, Aug 18, 2023 at 10:45 AM Rogan Dawes <rogan at dawes.za.net> wrote:
>
> Circling back to this, I wanted to get a modern u-boot running on the
> Wink Hub v1 as well. Since it is possible to invoke SDP over USB
> (having soldered on a suitable microUSB connector), I have no concern
> about bricking it now. It's also a LOT easier than JTAG!
>
> I tried to build and flash the mx28evk_defconfig, but failed to get
> any output on the serial console. This is likely to be unsurprising,
> due to the already established alternative configuration of the UART
> identified by Fabio.
>
> I then patched imx28.dtsi to add duart_pins_c as per Fabio's previous
> patch for the Linux kernel:
>
> + duart_pins_c: duart at 2 {
> + reg = <2>;
> + fsl,pinmux-ids = <
> + MX28_PAD_I2C0_SCL__DUART_RX
> + MX28_PAD_I2C0_SDA__DUART_TX
> + >;
> + fsl,drive-strength = <MXS_DRIVE_8mA>;
> + fsl,voltage = <MXS_VOLTAGE_HIGH>;
> + fsl,pull-up = <MXS_PULL_DISABLE>;
> + };
> +
>
> And updated mx28evk_defconfig to use duart_pins_c instead of
> duart_pins_a. However, I still got no output after using:
>
> sudo $(which snagrecover) --soc imx28 -f
> src/snagrecover/templates/imx28-evk.yaml

I am not familiar with this tool. I was only aware of the one below:

https://source.denx.de/denx/mxsldr

Are you able to load the original vendor U-Boot with it?

Also, is the original vendor U-Boot source code available?

It is important to re-use the same DDR initialization from the original U-Boot.

> with u-boot.sb in the current directory.
>
> I also tried using the complete imx28-wink-hub-v1.dts as created by
> Fabio, and updated the .config to reference that instead of the
> imx28-evk, but I suspect that I may not have made the updates
> sufficiently well, if the name of the board needs to correspond with
> any details of the device tree? Neither of these resulted in any
> output.
>
> Any other suggestions?

Please check board/freescale/mx28evk/iomux.c:

const iomux_cfg_t iomux_setup[] = {
/* DUART */
MX28_PAD_PWM0__DUART_RX,
MX28_PAD_PWM1__DUART_TX,

The DUART pins need to be changed here as well.